1. Field of the Invention
The present invention relates to a dielectric ceramic composition and a multilayer ceramic capacitor including the same, and more particularly, to a dielectric ceramic composition having a high dielectric constant and excellent high-temperature reliability, and a multilayer ceramic capacitor including the same.
2. Description of the Related Art
In general, electronic components using a ceramic material, such as a capacitor, an inductor, a piezoelectric element, a varistor, a thermistor, or the like, include a ceramic body formed of a ceramic material, internal electrodes formed within the ceramic body, and external electrodes provided on surfaces of the ceramic body and connected to respective internal electrodes.
Among ceramic electronic components, multilayer ceramic capacitors include a plurality of stacked dielectric layers, internal electrodes disposed to face each other, having the dielectric layer interposed therebetween, and external electrodes electrically connected to respective internal electrodes.
Multilayer ceramic capacitors have been widely used as components in mobile communications devices such as computers, personal data assistants (PDAs), mobile phones, and the like, due to advantages thereof such as a relatively small size, high capacitance, ease of mounting, and the like.
A multilayer ceramic capacitor is manufactured by using a paste for internal electrodes and a paste for dielectric layers in a sheet method, a printing method, or the like, and simultaneously sintering the stacked sheets of paste.
However, in the case of a dielectric material used in the multilayer ceramic capacitor according to the related art, or the like, when the dielectric material is sintered under a reducing atmosphere, the dielectric material may be reduced to thereby become a semiconductor.
For this reason, as a material for internal electrodes, a noble metal such as palladium (Pd), or the like, which may not be melted at a temperature at which the dielectric material is sintered and may not be oxidized even in the case of being sintered at a high oxygen partial pressure at which the dielectric material does not become a semiconductor, is used.
However, since a noble metal such as palladium (Pd), or the like, is relatively expensive, the noble metal may significantly increase manufacturing costs of the multilayer ceramic capacitor.
Therefore, as the material for internal electrodes, a base metal such as nickel (Ni), a nickel alloy, or the like, which is relatively inexpensive, is mainly used.
However, in the case in which the base metal is used as a conductive material in the internal electrodes, the internal electrodes may be oxidized in the case of sintering the internal electrodes under an air atmosphere.
Therefore, the dielectric layers and the internal electrodes should be simultaneously sintered under the reducing atmosphere.
However, when they are sintered under the reducing atmosphere, the dielectric layer may be reduced, such that insulation resistance (IR) may be decreased.
Therefore, a non-reducing dielectric material has been suggested.
Further, in the case in which barium titanate (BaTiO3) is used as a base material for the dielectric material, in order to suppress non-uniform grain growth and form uniform grains, a magnesium oxide (MgO) additive has generally been used.
However, the magnesium oxide (MgO) additive may be easily solid-solubilized in barium titanate (BaTiO3) to serve as an acceptor, such that there is a problem in terms of high-temperature reliability. Therefore, a solution for the problem has been required.
[RELATED ART DOCUMENT]
    (Patent Document 1) Korean Patent Laid-Open Publication No. 2002-0040610